Spinneret and spinning method



5, 1954 J. P. MIKA 3,131,428

SPINNERET AND SPINNING METHOD Filed Dec. 19, 1958 United States Patent Oilfice 3,131,428 Patented May 5., 1964 3,131,428 SPHWNERET AND SPINNING METHOD John P. Mika, Pearisburg, Va., assignor to Celanese Corporation of America, New York, N .Y., a corporation of Delaware Filed Dec. 19, 1958, Ser. No. 781,796 7 Claims. (Cl. 188) The invention relates to the manufiaoture of artificial or synthetic filaments or fibers, and is more particularly directed to filaments of novel cross-secion, and methods and means for making such filaments. Also, the invention relates to fabrics and other articles of manufacture, including non textile products, of yarn or tow including such filaments in either continuous filament or staple form.

A primary object of the invention is to provide bulky filamentary material of increased surface area and low pressure drop to afford improved filtration at low resistance to air fiow thereby making tow formed of such filaments particularly adapted for use in cigarette filters. Yarn of the filamentary material of the invention is also particularly suitable for use where it must be dyed as in upholstery textiles and carpeting applications, wherein the increased surface area produces more rapid penetration by dyestuffs.

A further object is to provide a resilient yarn having a high cross-section fidelity within each filament and between filaments so that dyeing and yarn physical properties will be uniform.

Another object of the invention is to provide improved methods for producing the novel filamentary materials.

Still another object of the invention is to provide a spinnerette having special jet openings or orifices formed therein for the manufacture of the novel filaments.

These, and other objects and advantages of the invention will be apparent from the following detailed description of the invention.

Generally, hollow filamentary material made in accordance with the invention is substantially .A- or H- shaped in cross-section. Both shaped filaments include two longitudinally extending channels, at least one of which is open to the outside. In the H-shaped filaments the second channel is also open to the outside while in the A-shaped filaments the second channel is substantially completely surrounded. The width of the filaments at the level of the cross-bars is approximately equal to the length of the sides. In the H-shaped filaments the ends of the sides approximately define a square. The converging ends of the sides of the A-shaped filaments do not meet in a. point but rather just barely touch so that the width of the filament across the top is approximately twice the Width of each side. The web-shaped cross-section is responsible for a high ratio of cross-sectional periphery to area which in turn means a large surface for a given denier as compared with ordinary bulbous filaments.

Both types of filaments are resistant to bending and thus are especially suited for cigmette filters, upholstery, carpeting, stuffing, and the like, where resilience is desired. The bulk factor, i.e. the ratio of the area of the smallest circle which can circumscribe the filament to the actual filament cross-sectional area is less fior regular bulbous filaments than it is for the A-shaped filaments or for the H-shaped filaments. The filament bulk prevents close packing when they extend parallel to each other and are straight. When twisted into a yarn, however, the A-shapcd filaments pack tightly and produce fabrics of greater density and lower air permeability than fabrics identical except for the presence of regular bulbous filaments spun through round orifices. Both the A and H filaments give dye indices higher than for bulbous filaments of equal denier.

Filament-forming materials preferably employed in the practice of the present invention are the derivatives of cellulose such as the esters or others thereof, for example, cellulose organic acid esters such as cellulose acetate, cellulose propionaite, cellulose butyrate, cellulose benzoate, cellulose acetate formate, cellulose acetate propio nate, cellulose acetate butyuate and the like, ethyl cellulose, etc. The esters may be ripened and acetonesoluble, such as conventional cellulose acetate, or may be substantially fully esterified, that is, contain fewer than 0.29 firee hydroxyl groups per anhydroglucose unit, e.g. cellulose triacetate.

The filament-fiorrning material may also comprise other thermoplastic or solvent-soluble polymeric materials such as super-polyamicles, e.g. nylon; superpolyesters such as polyethylene terephthalate, polyglycolic acid and copolymers thereof; aoryloni-trile polymers and copolymers, polymers and copolymers of olefins and vinyl esters such as ethylene, propylene, vinyl chloride, vinylidene chloride, vinyl acetate, and the like.

The filament-forming material is initially in liquid phase, e.g. a solution of the filament-forming material in a volatile solvent is extruded through the jet openings of a spinnerette into an evaporative atmosphere, and the resulting filaments are preferably taken up at a linear speed of about to 700 and preferably 200 to 500 meters per minute. The take-up speed may range from about 0.6 to, 1.4 and preferably 0.9 to .2 times the linear speed at which the solution is extruded through the jet openings. When dry spinning a solution of secondary cellulose acetate in acetone the temperature of the dope being extruded generally ranges from about 40' to C.

In making filamentary material of the construction hereinbefore described by dry spinning, a novel form of spinnerette is used. The spinne-ret-te is provided with jet openings having four sides, one pair of opposite sides being concave in a direction away from the interior of the ope ing. For H-shaped filaments the other pair of opposite sides is substantially straight While for A-shaped filaments the other pair is convex in a direction away trom the interior of the opening. In a preferred embodiment the concavities and convexities are arcualte and generally a proximately circular arcs.

For producing Hshaped filaments the periphery of each opening is approximately defined by a square one pair of opposite sides of which are rendered concave in a direction away from the interior of the opening. The distance from. concavity to concavity may range from about 30 to 60% and preferably about 48 to 52% of the length of a side of the square. Preferably the concavities are defined by substantially semi-circular arcs, and the straight sides are parallel. If the straight sides are canted too far toward one another rather than being parallel the resulting filament will be A-shaped.

For producing A-shaped filaments the periphery of each opening is approximately defined by a circle provided With a pair of opposed arcuate concavities. The distance from concavity to concavity may range from about 30 to 60% of the length of the diameter of the circle. Preferably the concavities are defined by arcs of circles and the opposed arcs are not identical.

The denier of each filament produced may be 55 or more but generally ranges from about 2 to 25 and preferably from about 3 to 16. Large bundles or tows of the filaments can be spun directly or many smaller bundles can be gathered into a single large bundle for further processing in conventional manner. Prior to such further processing, the bundle of filaments may be subjected to treatment to increase its bulk, as by air jet 3 bulking or crimping, e.g. to impart about to 20 and preferably 7 to 12 crimps per inch.

The invention will now be described more fully with reference to the accompanying drawing, wherein:

FIG. -1 is a cross-section on an enlarged scale through filamentary material produced in accordance with one embodiment of the invention;

FIG. 2 is a view of the face of a spinnerette having jet openings or orifices arranged therein to furnish filamentary material having the cross-section illustrated in FIG. 1;

FIG. 3 is a greatly enlarged view of a single jet opening for forming a single filament as shown in FIG. 1;

FIG. 4 is a cross-section on an enlarged scale through filamentary material produced in accordance with another embodiment of the invention;

FIG. 5 is a view of the face of a spinnerette having openings therein which furnish the filamentary material having the cross-section illustrated in FIG. 4;

FIG. 6 is a greatly enlarged view of a single jet opening for forming a single filament of the contour shown in FIG. 4;

FIG. 7 is a cross-section on an enlarged scale through filamentary material made up of a mixture of A- and H-shaped filaments;

FIG. 8 is a View of the face of a spinnerette for forming the filamentary material in FIG. 7; and

FIG. 9 is a view of a cigarette having a filter including the novel filamentary material.

Referring now more particularly to the drawing, in FIG. 1 there is shown in cross-section a plurality of filaments 10 each being H-shaped with the sides of the H curved outward slightly.

In making filaments having the construction shown in FIG. 1 of a cellulose organic acid ester, the usual system or dry spinning system for converting cellulose organic ester solutions into filament is well-known, and need not be illustrated and described here. The spinnerette, however, is fornred with novel openings or orifices.

As shown in FIG. 2, each of the filaments 10 is produced by a spinnerette 12 formed with openings 14. While the spinne-rette is shown as provided with three openings, the number of openings could be as many as 300 or more. FIG. 3 shows in detail the shape of one of the openings 14 used in Example I hereinbelow. The opening 14 is defined by a pair of substantially parallel 7 sides 16, 18 of equal length and spaced from each other by a distance approximately equal to their length. Connecting the sides 16, 18 at opposite ends is a pair of opposed concave sides 23', 22. Sides 20, 22 include substantially circular arcs 24, 26 having a radius of curva ture about 20 to 35% of the length of side 16, the distance from 24 to 26 being about 30 to 60% and preferably about half the length of side '16. The sides 20, 22 are completed by portions 23 which are straight adjacent sides 16, 18 and then curved slightly to merge smoothly with arcs 24, 26.

Spinning under identical conditions through spinnerettes having square jet openings will produce a bundle in whose cross-section some filaments are more or less H-shaped, a greater number are X-shaped and a still greater number are distorted, being neither a true H or X. For example, about will be H, 40% will be X and 45% will be distorted to some intermediate shape. The novel jet openings, however, produces almost all of which are of true H-shape substantially along their whole lengths. Also all the legs of each filament will be of substantially equal size so that there is symmetry within a single filament cross-section and uniformity along each filament with all filaments being substantially identical. T his uniformity in turn produces uniform dyeings with obvious advantage.

In the form of the invention illustrated in FIG. 4, the filaments '30 are each substantially A-shaped, comprising a pair of substantially straight sides 32, 34 that iust touch at their tops to form with cross-bar 36 a closed channel 38 extending longitudinally of the filament. The opposite ends of sides 82, 34 are spaced from each other and define, with cross-bar 36, an open channel 40 also extending longitudinally of the filament. The widths of sides 32, 34 and of cross-bar 36 are approximately equal. The length of cross-bar 36 between sides 32 and 34 is about 40 to 60% and preferably 45 to 55% of the length of sides 32 34. The cross-bar 36 is connected to the sides somewhat closer to their spaced ends than to their abutting ends. The width of the filament across the spaced ends is approximately equal tothe length of sides 32, 34.

The filaments 30 are produced by a spinnerette 42 having a plurality of openings 44 such as shown in FIG. 5', one being shown on a more enlarged scale in FIG. 6. Each opening 44 includes a pair of opposed circular convcxities 46, 48 each subtending an angle of about 70 to and preferably about 82 to 88. Connecting ccnvexities 46, 48 are a pair of c oncavities 5t}; 52 which are approximately arcs of a circle having a diameter ranging from about 70 to and preferably 95 to 105% of the diameter of the circle defining the convexities. The distance from 50 to '52. ranges from about 30 to 70% and preferably 40 to 50% of the diameter of the circle defining the convexities. The distance from St} to the center of the circle defining convexities 46, 48 should be about 5 to 20 and preferably 10 to 15% greater than the distance from 52 to said center if well-defined A- rather than H-shaped filaments are to be produced. The joinder between the ends of the convexities and concavities may be rounded slightly for ease of manufacture and to produce filaments having sides correspondingly rounded at their ends in cross-section.

FIG. 7 shows a yarn 54- composed of filaments 10 of H-shaped cross-section and filaments 3d of A-shaped cross-section, which yarn possesses a large surface area and a very high bulk. The yarn 54 of FIG. 7 is obtained by extrusion through a spinnerette '56 as shown in FIG. 8 having openings -14 and 44-. In place of openings of the type shown in FIGS. 3 and 6 both provided in the same spinnerette, a spinnerette may be provided with either of these types of openings in addition to round, triangular, etc. openings to produce a yarn having the indicated shape of filaments mixed with filaments of bulbous, Y, etc. cross-section.

FIG. 9 sh ws a cigarette 58 including a filter 60 com-' An acetone solution of secondary cellulose acetate,

having an acetyl value of 55%, is extruded at a linear speed of 390 meters per minute downwardly into a cabinet through a spinnerette provided with openings as shown in FIG. 3, the sides 16 and 18 being 0.054 mm. long, arcs 24, 26 being semi-circular and having a radius of curvature of 0.014 mm, the arcs being spaced from each other by 0.026 mm. Air at room temperature is passed downwardly through the spinning cabinet. The resulting yarn is taken up at a linear speed of 405 meters per minute and has a denier of 625. 118 such yarns are joined into a bundle or tow and are passed through a stufiing box crimper to impart an average of about 8 I crimps per inch. The tow is opened in conventional manner, sprayed with 8% of its weight of glycerine triacetate as a plasticizer and formed in a filter rod or" 79,000 total denier (taking into consideration the increase resulting from the crimping). The rod is cured at room' temperature for 2 hours to cause adhesionof the filaments at points of contact, in conventional manner, cut into 15 mm. plugs and wrapped with tobacco into filter tip cigarette's on conventional cigarette forming machines.

Instead of using it in cigarette filters, the individual 625 denier 5 denier per filament yarn can be air jet bulked for use in upholstery or carpet construction, or it may be cut into high bulk staple preferably following crimping.

The individual filament in cross-section has a bulk factor of 1.64 whereas that for a 5 denier filament spun through a round opening is 1.28. Its dye index is ap proximately ten units higher than for a filament of equal denier spun through a round opening. The dye index is a measure of the degree to which a cellulose acetate yarn specimen picks up Celliton Fast Blue AF from a standard dyebath under standard dyeing conditions. The dyed yarn specimen is dissolved to a predetermined concentration in acetone and the light transmittancy of the solution is measured under predetermined conditions. The dye index equals 100 times the optical density of a solution in ml. of acetone of 30 meters of filament, measured in a cell 1.00 cm. thick at a wave length of 615 m Example 11 By the process of Example I the same dope is spun through a spinnerette having 17 openings such as shown in FIG. 6, i.e. a diameter of 0.054 mm. for arcs 46, 48, 50 and 52, arms 46 and 48 subtending 85 each and are 52, 50 being 12% more distant than are 50 from the center of the circle defining arcs 46 and 48. The resulting 4.5 denier per filament yarn is taken up with 0.2 turn per inch and processed into fabric. A peculiar effect is noted in that the fabric has higher than normal light transmission, but lower than normal air permeability. This is attributed to the tendency for the particular section to yield a flattened rather than a round filament bundle.

The individual filament has a dye index 10 units greater than regular filaments. When this particular type filament is twisted into yarn, the characteristic bulkiness of the individual fibers is replaced with denseness in the yarn. This change is obtained when the individual filaments pack together to form a yarn which is denser than yarn made from bulbous filaments. Nonetheless dyeing is more rapid.

It is to be understood that the foregoing detailed description is given merely by way of illustration and that many variations may be made therein without departing from the spirit of my invention.

Having described my invention what I desire to secure by Letters Patent is:

1. A spinnerette having at least one jet opening having four sides, one pair of opposite sides being substantially straight and equal in length, the other pair of opposite sides being circular arcs concave in a direction away from the interior of said opening and having a radius of curvature about 20 to 35% of the length of one of said straight sides.

2. A spinnerette having at least one jet opening having four sides, one pair of opposite sides being convex in a direction away from the interior of said opening and lying approximately on the circumference of a circle and each subtending an angle of about 70 to 100, the other pair of opposite sides being concave in a direction away from the interior of said opening and being approximately arcs of a circle having a diameter of about 70 to 120% of the diameter of said first-named circle.

3. A spinnerette having at least one jet opening having four sides, one pair of opposite sides being straight, substantially parallel and spaced from each other by a distance approximately equal to the length of said sides, the other pair of opposite sides being concave in a direction away from the interior of said opening and being spaced from each other a distance ranging from about 30 to of the length of one of said straight sides.

4. A spinnerette having at least one jet opening having four sides, one pair of opposite sides being convex in a direction away from the interior of said opening and lying approximately on the circumference of a circle and each subtending an angle of about to the other pair of opposite sides being concave in a direction away from the interior of said opening, being spaced from each other a distance ranging from about 30 to 70% of the diameter of the circle defining said convex sides and being spaced unequal distances from the center of the circle defining said convex sides.

5. The method which comprises extruding a filamentforrning material in liquid phase through at least one opening having four sides, one pair of opposite sides being substantially straight and equal in length, the other pair of opposite sides being circular arcs concave in a direction away from the interior of said opening and having a radius of curvature about 20 to 35% of the length of one of said straight sides, thereby to form filamentary material having a large surface area.

6. The method which comprises extruding at a temperature of about 40 to C. a solution of cellulose acetate through at least one opening into an evaporative atmosphere, said opening having four sides, one pair of opposite sides being substantially straight and equal in length, the other pair of opposite sides being concave in a direction away from the interior of said opening and being spaced from each other a distance ranging from about 30 to 60% of the length of one of said straight sides, thereby to form filamentary material having a large surface area, and taking up the resulting filamentary material at a linear speed about 0.6 to 1.4 times the linear speed of extrusion through said opening, thereby to form filamentary material having a large surface area.

7. The method which comprises extruding at a temperature of about 40 to 110 C. a solution of cellulose acetate through at least one opening into an evaporative atmosphere, said opening having four sides, one pair of opposite sides of said opening is convex in a direction away from the interior of said opening and lies approximately on the circumference of a circle, each subtending an angle of about 70 to 100", the other pair of opposite sides being concave in a direction away from the interior of said opening, being spaced from each other a distance ranging from about 30 to 70% of the diameter of the circle defining said convex sides, and taking up the resulting filamentary material at a linear speed about 0.6 to 1.4 times the linear speed of extrusion through said opening, thereby to form filamentary material having a large surface area.

References (Iited in the file of this patent UNITED STATES PATENTS 414,090 Taylor Oct. 29, 1889 817,085 Moshier Apr. 3, 1906 1,613,940 Copen Jan. 11, 1927 1,964,659 Brumberger June 26, 1934 2,373,892 ickey Apr. 17, 1945 2,439,039 Coe Apr. 6, 1948 2,780,833 Braunlich Feb. 12, 1957 2,825,120 Smith Mar. 4, 1958 2,828,752 Jackson Apr. 1, 1958 2,831,748 Finlayson et al Apr. 22, 8 2,891,277 Sutor June 23, 1959 

1. A SPINNERETTE HAVING AT LEAST ONE JET OPENING HAVING FOUR SIDES, ONE PAIR OF OPPOSITE SIDES BEING SUBSTANTIALLY STRAIGHT AND EQUAL IN LENGTH, THE OTHER PAIR OF OPPOSITE SIDES BEING CIRCULAR ARCS CONCAVE IN A DIRECTION AWAY FROM THE INTERIOR OF SAID OPENING AND HAVING A RADIUS OF CURVATURE ABOUT 20 TO 35% OF THE LENGTH OF ONE OF SAID STRAIGHT SIDES. 